Beam Recovery Timer Logic for Radio Link Failure Handling
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Solution Overview
Problem
In the 3GPP NR system, particularly in high frequency bands, there is a challenge in performing Radio Link Monitoring (RLM) and Radio Link Failure (RLF) detection and handling at the beam level, as existing mechanisms are not adequately designed to manage beam-level failures and recoveries effectively.
Innovation Solution
The proposed solution involves using periodic in-sync and out-of-sync indications between Layer 1 and Layer 3 to trigger timer-based procedures for beam recovery and RLF handling, where Layer 3 initiates beam recovery procedures based on consecutive out-of-sync indications and attempts RRC connection re-establishment when beam recovery fails, utilizing timers T1, T2, and T3 to manage these processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beam-level RLM and RLF handling mechanisms are implemented in 3GPP NR system, then communication reliability is improved, but system complexity increases due to additional timer-based procedures and layer interactions
Solution Approach 1:
The patent segments the RLM and RLF handling into distinct timer-based procedures (T1 for failure detection, T2 for recovery attempts, T3 for re-establishment) and separates Layer 1 channel quality indications from Layer 3 control decisions. This segmentation allows independent optimization of each component while maintaining overall system reliability without excessive complexity.
Solution Approach 2:
The patent implements preliminary actions by pre-configuring multiple timers (T1, T2, T3) with specific functions: T1 prepares for failure detection before it occurs, T2 pre-establishes recovery procedures before beam failure happens, and T3 readies re-establishment mechanisms in advance. This preliminary preparation enables rapid response to beam failures without ad-hoc decision-making, improving reliability while keeping complexity manageable through structured pre-planning.
2Speed
If timer-based procedures are used for beam recovery and RLF handling, then response speed is improved, but time consumption increases due to multiple timer expirations and procedure iterations
Solution Approach 1:
The patent employs periodic action through Layer 1 periodically providing channel quality indications to Layer 3, and Layer 3 periodically checking timer statuses and triggering appropriate procedures. This periodic monitoring ensures rapid detection of beam failures while the structured timer sequence (T1→T2→T3) minimizes unnecessary iterations by progressing systematically through recovery stages only when needed, balancing response speed with time efficiency.
Solution Approach 2:
The patent implements feedback mechanisms where Layer 1 continuously feeds channel quality information to Layer 3, and Layer 3 feeds back control decisions based on timer expirations and recovery outcomes. This closed-loop feedback enables the system to adapt quickly to beam failures by triggering appropriate procedures only when actual degradation is detected, improving response speed while avoiding wasteful time consumption through targeted rather than blanket retransmissions or re-establishment attempts.
3Reliability
If beam recovery procedures are triggered multiple times, then recovery reliability is improved, but device operation complexity increases due to counter management and procedure repetition
Solution Approach 1:
The patent applies preliminary action by pre-configuring a maximum retry counter before beam recovery procedures begin. This counter is established in advance with a predetermined threshold, allowing the system to automatically limit recovery attempts without complex real-time decision-making. The preliminary setup simplifies operation by providing clear, pre-defined rules for when to retry and when to escalate to RRC re-establishment, improving recovery reliability through systematic retries while maintaining ease of operation through simple counter-based control.
Solution Approach 2:
The patent uses feedback through the counter mechanism that tracks the number of beam recovery procedure attempts. Each failed recovery incrementally updates the counter, providing feedback that guides subsequent actions: if the counter reaches the predetermined maximum, the system automatically transitions to RRC connection re-establishment. This feedback-driven approach improves recovery reliability by persisting through transient failures while simplifying operation through automatic, rule-based escalation without requiring complex manual intervention or analysis.
Data Source
AI summary
Apparatuses of wireless communication devices are disclosed. An apparatus of a user equipment includes one or more processors configured to start a first timer responsive to detection of a Radio Link (RL) failure, start a second timer and trigger a beam recovery procedure one or more times responsive to expiry of the first timer if RL recovery is not detected, and start a third timer and attempt to find a suitable cell for Radio Resource Control (RRC) connection reestablishment responsive to one or more expiries of the second timer if RL recovery fails. The one or more processors are also configured to go to an RRC idle or inactive state responsive to expiry of the third timer if a suitable cell for RRC connection reestablishment is not found.